Many substances can be classified as either an acid or a base. Lemon juice is a weak acid and like most acids, it tastes sour. A base is the opposite of an acid.
A pH is a was to measure how acidic or base a liquid is. The value ranges from 0 and 7 for an acid and 7 to 14 for a base.
Some strong acids and bases can attack and irritate your skin, so you need to be careful.
This is a simple experiment to find out if a liquid is an acid or a base.
You will need:
half a red cabbage
some glasses or clear plastic cups
two jugs or medium sized bowls
a couple of teaspoons
test liquids – we used lemon juice, vinegar, apple cider vinegar, coco-cola, soda water, bi-carb soda, salt, washing detergent, washing-up detergent, liquid soap, rubbing alcohol, and dettol
What to do:
Cut the cabbage into small pieces and place in the jug / bowl.
Cover the cabbage with boiling water and let it sit for 10 minutes. You could also use cold water, but you will need to let it sit for 45 minutes.
Strain the juice into another jug/bowl. This purple cabbage juice is your indicator and it is ready to use.
Pour equal amounts of the indicator into each of the glasses / plastic cups.
Slowly add your test liquids, one to each of the plastic cups.
Mix in the salt and the bi carb soda with a teaspoon.
The liquids should mix as they are poured in.
What happens to the colour of the indicator / cabbage water?
Our boys completed this worksheet, making their hypothesis before adding the solution to each of the cups.
You can download your free copy below:
Explanation: Red cabbage juice contains chemicals that change colour when mixed with certain other chemicals. When you add an acid to the cabbage juice, it will turn to a different shade of red, but when you add a base to the liquid, it will change to a blue or green colour.
What are some other solutions you could use when doing this experiment?